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Very helpful Barry. Thanks for the write up.

Great article Barry!

I'm going to need to read this article 40 times.

great article as always - here is a different angle on it that might help people understand

once you take all the info above in - you will see that a FF has over 6 stops that it can open up over a 1/4 inch on an equivalent shot to reduce DOF. This is why DOF is so much shallower on a larger format. Its the equivalent shot thats important. Cause if you just use the same mm lens and same COC you will have the same DOF. But you need a different lens and since you then have more "room" to open up on the larger format to reduce DOF you will be able to get a shallower shot

maybe that wasnt any clearer

This was posted over on Reduser the other day. Interesting perspective on the much debated DOF:

http://blogs.digitalmediaonlineinc.c...entry/20090920

Great article Barry. When I get my 7D, I'm going to do my best not to shoot at anything wider than f5 or f6. This should be easy for me as I shoot action sports outdoors. I really dislike how the super shallow DOF seen from these DSLRs is making some people say they have a "cheesy DSLR look". In my opinion, this "cheesy look" from these cams is solely due to people's infatuation with super shallow depth of field which results in an unflattering and aesthetically unappealing image.

Very helpful. Thanks.

So... at 10ft, with a 2/3 sensor, what would the DOF be at f2 with a 35mm lens?

-r

Consult an online depth-of-field calculator, such as this one:
http://panavision.co.nz/main/kbase/r...alcFOVform.asp

It says there will be 2' 1" of DOF.

This is probably the first article ever in a video forum that gets DOF to the right direction, although the preset values in calculators are not consistent, sometimes being anything from 16:9, 4:3 3:2.

If everything is the same (camera position, scene, distance of focus, angle of view), you just need the same ABSOLUTE aperture diameter in mm in order to get identical results. The same angle of view is achieved when you divide the focal length with the crop factor. The same absolute aperture size is achieved when the relative f stop number is divided by the crop factor.

So, 2/3" 10mm lens f2.8 matches 1/3" 5mm lens f1.4. Crop factor is 2 on this case.

Focal lenght/crop factor provides same angle of view, framing and perspective from the same point. The 10mm becomes 5mm. Relative aperture/crop factor provides same DOF, f2.8 becomes f1.4, because the absolute aperture diameter is matched (10/2.8 = 5/1.4 = 3.57mm diameter).

You are simply imaging the same angle of view, through an aperture of the same size. You are projecting the same world through the same optical method to two different distances, one closer (1/3" sensor 5mm away, 2/3" sensor 10mm away). It's like moving the projector in a home theater system and adusting the viewing distance so that you get the same view in your eyes. You are not going to change the directors vision

Your screen will be brighter in the projection from the smaller distance though but that's another story, and related to sensors, a very complex one.